Your clinician mentions a musculoskeletal ultrasound, and the name is a mouthful. Here is the plain version of what it is for.
The short answer
Musculoskeletal ultrasound is a diagnostic scan. RadiologyInfo.org describes it this way: "It is used to help diagnose sprains, strains, tears, trapped nerves, arthritis and other musculoskeletal conditions."
A sprain, a strain and a tear all appear on that list.
Where it sits next to other scans
You do not have to choose the scan yourself. Your clinician does that. If you hear about a different scan, MedlinePlus has pages on a leg MRI scan and on a joint x-ray, so you can read about each one before the appointment. RadiologyInfo.org also has its own page on musculoskeletal ultrasound.
Bringing one clear question to the scan
Write down the question you want the scan to answer, such as whether a sprain is a tear. That note costs nothing and needs no training. Bring it to the appointment. Readers in and around Wood Dale can use the same approach: go in with one clear question and ask which scan fits it and why.
A note for a first-timer
Medical imaging can feel like a lot of unfamiliar terms. You only need to know what the scan is for, and RadiologyInfo.org gives that in one sentence.